American Mineralogist, Volume 70, pages 1050-1055, 1985

The crystal structureof wroewolfeite,a mineral with lCu+(OH)e(SO4XH2O)lsheets

F. C. H,C.WTHORNEAND L. A. GNOET Departmentof Earth Sciences,Uniuersity of Manitoba Winnipeg,Manitoba, Canqda, R3T 2N2

Abstract The of wroewolfeite,Cun(SOa[OH)6'2H2O, monoclinic, a : 6.0a5(1), b : 5.646(1),c : A.337Q)A,B :93.39(l)', / : 488.5(1)A3, Pc, has beensolved by direct methods and refined by full-matrix least-squaresto an R index of 6.7% usingTll observed(I > 2.5o\ reflections measuredon a twinned crystal. The fundamental building block of the wroewolfeitestructure is a [Cun(SOnXOH)rr]t- hetropolyhedralcluster that polymerizesin two dimensionsby edge-sharingbetween octahedra to form the structure module, a [Cu4(SO4[OH)6(H2O)]' sheet that is parallel to {001}. These sheetsare linked solely by hydrogenbonding, involving an additional (HrO) anion that is not directly bonded to a cation. This [Cu4(SO4XOH)6(H2O)]'sheet is also found in and may also occur in langite.This and other related sheetsmay be describedby the generalformula [MoX,d.-.], in which M : octahedrallycoordinated cation, X : complex anion, @: simple anion (e.g' O'z-, (OH)-, (HrO)").Thefollowing structures are included: n : 0, botallackite;n : 1,wroe- wolfeite,langite, posnjakite; n :2, ktenasite,, devillite. The intra-module linkages and hydration states in these minerals may be interpreted in terms of the Lewis ba- sicity/acidityof structural fragments.

Introduction tube and a highly oriented graphite crystal monochromalor mounted with equatorial geometry. A random orientation photo- Wroewolfeiteis a monoclinic hydrated copper hydroxyl graph showed many of the reflections to occur as pairs with an sulphateCun(SOn[OH)6.2H2O, first describedby Dunn intensity ratio of -3: 1. Twenty-five reflections were centered, and and Rouse (1975) from the Loudville lead mine, the correct unit cell was selected from an array of real space Loudville, Massachusetts.They assignedit to the same vectors corresponding to potential unit cell axes. Twenty-three of group as posnjakite,Cun(SOn[OH)u.HrO, and langite, the twenty-five reflections had integral indices; the rernaining re- Cuo(SOo[OH)6'2H2O,and it is presumablydimorphous flections were discarded as being from an alternate twin compo- with langite. nent. Additional reflections were centered and indexed, until the twenty-five reflections were all from the same twin component. Least-squares refinement of these reflections produced the mono- Experimental clinically constrained cell dimensions given in Table I, together Thematerial used in thisstudy is from theLoudville lead mine, with the orientation matrix relating the crystal axes to the diffrac- Loudville, Massachusetts, and was obtained from the Department tometer axes. of Mineralogy and Geology, Royal Ontario Museum, collection Intensity data were collected in the 0-20 scan mode, using 96 - number M37058. Single-crystal X-ray precession photographs in- steps with a scan range from [20(MoKdt) 1]' to f20(MoKar) dicate monoclinic symmetry, with systematic absences ld)l; * 1]" and a variable scan rate between 4.O and 29.3'lmin depend- l:2n + 1, consistent with space groups P2/c and Pc. The ob- ing on the intensity of an initial one second count at the center of served cell dimensions are in good agreement with the values the scan range. Backgrounds were measured for half the scan time reported by Dunn and Rouse (1975). The crystals are twinned by at the beginning and end of each scan. Two standard reflections reflection on {001}, leading to overlap on reflections of the type were monitored every 48 measurements to check for stability and 4h'k'1. This overlap is not merohedral; there is a distinct misre- constancy of crystal alignment. A total of 2588 reflections were gistry of the reflections. This twinlaw was reported by Dunn and measured over two asymmetric units out to a maximum 20 of 55". Rouse (1975). However, there is additional twinning evident in the Ten strong reflections uniformly distributed with regard to 20 (h0l) zeroJevel photograph, namely twinning by reflection on were measured at l0' intervals of Y (the azimuthal angle corre- {100}. Note that this twinning occurs for each member of the sponding to rotation of the crystal about its diffraction vector) plate {001} twin, resulting in four individual twin components. The rela- from O-350'. These data were used to calculate a thin em- tive amounts of the twin components were estimated as approxi- pirical absorption correction, the R (symmetric) index being re- mately 7O:25:4: I for the crystal used in the collection of the duced from 10.0% to 2.2% for the azimuthal data. This correction X-ray intensity data. was then applied to the whole data set, minimum and maximum The crystal was mounted on a Nicolet R3m automated four- transmission being 0.374 and 0.728 resepectively and the merging circle difractometer equipped with a molyMenum-target X-ray R (symmetric) being 2.3%. The data were also corrected for Lo- 0003{n4x/85/09l0-1050$02.00 1050 HAWTHORNE AND GROAT: STRUCTU RE OF WROEWOLFEIT E r051

Table 1. Miscellaneousinformation concerninswroewolfeite Structural description There is one unique S position in wroewolfeite;the S is a 6.045(l)R crystal size(m) O.O3x0.1zxo.l6 coordinatedby four 02- anions,the resulting tetrahedron b 5.646(l) RadlMono l'1olcr showing a typical range of bond lengthsand bond angles. c 14-337(2) Total lFoJ 1104 Thereare threelong S-O bonds,(S-O) :1.494, and one 6 93.39(l)o lrol '4 o 1008 short S-O bond, S-O : t.43A; this correlateswell with the V 488.5(l)R3 Non-overlappedlFol 7ll local bond-valencerequirements according to the hydrogen

Space Group Pc Final R (obs) 6.7% bonding schemeproposed later. There are four unique Cu positions,each Cu being coordinatedby six anions in dis- Final Rw(obs) 6.2% torted octahedral arrangements.Cu(l) is coordinated by unit cell contents: 2[CuO(S0O)(0H)U'2Hrol one 02- and five (OH)t- anions,with four short meridio- - R = t(lFo-lFcl)/tlFol nal bonds and two longer axial bonds to one (OH)l and one O2-. Cu(2)is coordinatedby five (OH)- anionsand R" = [rw(lFo -lF. 12twr!]!, r=t one (HrO)' molecule, with four short meridional bonds and two longer axial bonds to an (OH)- and the (HzO)" molecule.Cu(3) and Cu(4) are both bonded to one 02- - anion and five (OH)l anions, again with similar distri- rcnl4 polaization and background effects, averaged and reduced butions of bond lengths.Thus eachof the Cu{u octahedra to structure factors. Of the 1104 unique reflections, 1008 were (where @: O2-, OH-, H2O) show typical Jahn-Teller classed as observed (l F"l < 4o). distortions involving strong extension of the axial Cu-f bonds. Solution and refinement The structure of wroewolfeiteis illustrated in Figures I Scatteringcurves for neutral atoms togetherwith anom- and 2. The fundamentalbuilding block (FBB) of the struc- alous dispersioncoefncients were taken from Cromer and ture (Hawthorne,1985a) is the [Cun(SOn[OH)rr]e- he- Mann (1968)and Cromer and Liberman (1970).R indices teropolyhedral cluster that is repeated by simple trans- are of the form given in Table I and are expressedas lation along a andb. This links, by octahedraledge-sharing percentages. in both directionsto form the structuremodule pictured in In the first stageof structuresolution, the overlap due to Figure 1, an infinite sheetof edge-sharingCu@, octahedra twinning was disregarded.The structure was solved by with projecting (SO4) tetrahedra; this has the formula direct methods.The distribution of E-valueswere charac- [Cuo(SOoXOH)r(HrO)]'.The structure module is elec- teristic of a non-centrosymmetricspace group, and thus the trostatically neutral, and adjacent sheetsare linked solely spacegroup Pc was adopted.The phaseset with the high- by hydrogen bonding, the proposed arrangement being est combinedfigure of merit gavea solution which eventu- shown in Figure 2. There is one unique (HrO) moleculein ally refined to an R index of -13%. The stereochemistry the structure that is not directlv bonded to a cation. How- of this model was rather nonsensical,and inspection of a differenceFourier map indicatedthe presenceof a twinned structure component.At this stage,reflections of the type Table 2. Atomic parametersfor wroewolfeite 4h. k. I were removedfrom the data set. A differenceFou- rier located the remaining anions, and subsequentrefine- y z u iso.

ment convergedto an R index of 6.7% for an isotropic Cu(l) 0 0.3311(4) l/4 0.9r(5) thermal model. The diffraction data still containeda small cu(2) 0.5020(5) 0.3212(4) 0.250r(2) t.0t(5) contribution from the {001} twin, leading to overlap on Cu(3) -0.2476(5) -0.1682(4) 0.?428(21 1.02(5) ftlc0;however, removal of thesedata did not significantly cu(4) 0.2474(5) 0.1734(4) -0.2572(2) r 08(5) -0.07980r) affect the refinement results. Becauseof the incomplete s 0.0358(9) 0.035?(4) 1.43(8) o0 -0.0261(21 0.0098{27) 0.r376(9) r.4(3) data set (due to removalof partially overlapped ) ) reflections) 0(2) 0.1279125], 0.0012(30) -0.0132(r) 2.5{3) and residualeffects from other twin components.an aniso- 0( 3 ) -0.1607(24 ) 0.2811127 ) 0.0154(9) 1.8(3) tropic thermal model or refinementof H atom positions 0(4) -0.2443(?1) -0. l33l (33) 0.0052ilr ) 2.9(4) was not attempted.Final parametersare given in Table 2, 0(5)- 0.2525ile) 0.4991(2?l 0.r932(9) 0.8(2) observed and calculated structure factors are listed in o(6)r 0.2523(20) o-l4ol (23) 0.3052(8) 0.9(2) -0.?845123) Table 31 and interatomic distancesand anglesare given in 0{7)+ 0.0063(21) 0.3153(9) 0.9(2) 0.740609) 0.5073(2,]) 0.r894(9) 0.6(2) Table 4. An empirical bond-valenceanalysis is given in 0(8)+ 0(9)+ 0.7577120) 0.1470(24) 0.3076(9) 1.1(2) Table 5. o0o)+ 0.4s9r(t8) -o.o58t(21 ) 0.1753(8) 0.6(2) 0(lr)rr 0.5101(25) 0.6230(28) 0.373801) 2.r(3) ' 002)'. 0.2240127) 0.4638(30) -0.4964nr) 2.4(3) To receivea copy of Table 3, order Document AM-85-273 = from the BusinessOIIice, Mineralogical Societyof America,2000 n;. u,ro.xro2 Florida Avenue, N.W., Washington, D.C. 20009. Please remit tlndicates hydroxyl oxygens $5.00in advancefor the microfich. ttlndrcates water oxyqens 1052 HAWTHORNE AND GROAT: STRUCTURE OF WROEWOLFEITE

Table 4. Interatomicdistances (A) and angles(") in wroewolfeite Table 4. (cont.)

cu(l)-0(l) 2.425(15) Cu(2)-0(5) 1.950(12) 0(r0)-0( l ) 3.03(2) Cu(l)-0(5) 2.010('|2) Cu(2)-0(6) 2.022113], 00r)-0(3) 2.81l2l 0{r0)-0(4) 3.04(2) Cu(I )-0(6) 1.993(l2) cu(2 ) -0(8) 2.023112) 00r)-002) 2.77t2) cu0)-0(7 )a 2.36303) Cu(2)-0(9) 1.971(l3) 0il2)-0(2) 2.7012) Cu(l)-0(8)b 2.010(ll) Cu(2)-0( 0{12)-0(3) 2.7512]. cu(l)-0(9)b 2.013(13) Cu(2)-0(ll) 2.458(16) a: x, I +y, z; z-1/2; e: 2.136 2.136 I -y, z-l Cu(3)-0(I ) 2.306(14) Cu(4)-0(l)d 2.405(13) cu(3)-0{7) 1.918(12) Cu(4)-0(5)e 1.982(13) cu(3)-0(8)c L985('|2) cu(4)-0(6)d 1.982(13) Cu(3)-0(9)b 2.007(13) cu(4)-0(7)e 1.943(13) Cu(3)-0(10)b 1.917(il) Cu(4)-0(10)d 1.914(12) Cu(3)-0(11)c 2.718(16) Cu(4)-0(ll)e 2.648(15) ever,the (HrO) functionsas an anion and plays an integral 2.142 2.146 part in the proposed hydrogen bonding arrangement.As s-0(r ) 1.49205) (Tabl€ s-0(2) r.483(r7) can be seenfrom the bond-valencetable 5), O(1-4) s-0(3) r.49106) arc 02- anions,0(t-10) are (OH)t- anionsand O(11-12) s-0(4) L426il8) r.473 are (H2Of anions, and the hydrogen atom numbers indi- cate to which oxygen they are strongly bonded. H(5) and 0n )-0(5) 3.3r(2) 0(l)-cu(l )-0(5) 96.0(5 ) 0(r )-0(6) 2.94(21 0(1)-cu(l )-0(6) 83.0(5) H(11)B hydrogen bond to O(12) which hydrogenbonds to 0(1)-0(8)b 3.25(2) 0(1)-cu(l)-0(8)o 93.7(5) 0il )-0{9)b 2.94(2) 0(l)-cu(l )-0(9)b 84.7(4) O(2) and O(3),thus promoting inter-sheetlinkage and con- 0(5)-0(6) 2.59(2) 0(5)-cu(l)-0(5) 80.5(5) of the O(1-4) bond-valencere- 0(5) -0{7)a 2.6612t 0(5)-Cu(l)-0(7)a 74.5(5 ) tributing to the satisfaction 0(5)-0(8)b 3.09(2 ) 0(5)-Cu(l)-0(8)b 100.5(5 ) quirements.Note the approximately tetrahedral nature of 0(6)-0{7)a 3.58(2 ) 0(6)-cu(l)-0(7)a l]0.2(5) 0(6)-0(9)b 2.99(21 0(6)-cu(I ) -0(9)o 96.7(5) the bonds about the O(12) oxygen, an arrangementthat 0(7)a-0(8)b 2.6212) 0(7)a-cu{l)-0(8)b 73.2(5 ) 0(7)b-o{9)b 3.54(2 ) 0(7)a-cu(l)-0(9)b 107.9(5) seemsto be characteristicof this type of (HrO) anion. The 0(8)b-0(9)b 2.6s(2t 0(8)b-Cu(l)-0(9)b 82.215) remaining hydrogen atoms (H(G10) and H(l1)A) <0-0cu(l)> 3.01 <0-Cu{1)-0> 90.3 hydrogen-bond to 02- anions of the adjacent she€t,as 0(s)-0(6) 2.59(?l 0(5)-cu(2)-0(6) 81.2(5) in Figure 2. 0(5)-0{8) 2.96121 0(5)-cu{2)-0(8) e6.r(5) shown 0(5)-0( r0) 3.47l2l 0(5)-Cu(2)-0(l0) r05.6(5) This fairly weak linkage betweenthe sheetsaccounts for 0(5)-0{ r ) 3.0?(2t 0(5)-Cu(2)-0(ll) 85.8(5) 0(6)-0(9) 3.05(2) 0(6)-cu(2)-0{9) 99.8(5 ) the perfectcleavage on {001}; the reasonsfor the other two 0(6)-000) 2.66(2) 0{6)-Cu{2)-0(10) 73.6(5 ) 0(6)-o(l 1 ) 3.26(21 0(6)-cu(2)-0(II) 93.0(5) cleavages(on {100} and {010}) given by Dunn and Rouse 0(8)-0(9) 2.65t2t 0(8)-cu(2)-0(9) 83.0(s ) (L975) not might expect to be platy 0(8)-0(r0) 3.44t21 0{8)-cu(2)-0(10)106.r(5) are clear. One crystals 0(8)-0(rr ) 3.13(2) 0{8)-cu(2)-0(ll) 88.0(5 ) on however,the crystal usedin this study was platy 0(9)-0il0) 2.69\2) 0(9)-cu(2)-0{ l0) 75 215) {001}; o(9)-o(il ) 3.25t2], 0{9)-Cu{2)-0(ll) 93 6(5) on {010}. Again the reason for this is not at all clear. <0-0Cu{2) > 3.01 <0-Cu(2)-0> 90.I Conversely,it seemsrer$onable that the structure should 0(I )-0(7) 3.04{2 ) 0(I )-cu(3)-0{7) 9r.5(5) twin on {001}, as the hydrogenbonds should easily adjust 0(I )-0{8)c 3.27t2) 0{'l) -Cu(3)-0(8)c 99.215) 00 )-0{9)b 2.9412) 0(l)-Cu(3.)-0(9)b 85.s(5) to an alternatearrangement of adjacentsheets at the twin 0(r)-000)b 3.04(2) 0(I )-cu(3)-0( l0)b 91.5(5) plane.With regard to the twinning on could be 0(7 ) -0(8)c 2.62\2) 0(7)-cu( 3)-0(8)c 84.4(5 ) {100},.this 0(7) -0(9)b 2.8612) 0(7)-cu(3)-0(9)b 93.6(5 ) done by a 6" corrugation in the sheet,accompanied by a 0(7)-0{ll)c 3.2012) 0(7)-Cu(3)-0(ll)c 85.6(5 ) 0(8)c-0(10)b 2.95(2 ) 0(8)c-Cu(3) -0{ 10)b 9s.4(5) - 30' rotation of the sulphatetetrahedra. It is notable that 0(8)c-0(ll)c 3.r3(2) 0(8)c-Cu(3)-0(ll)c 8r.8(5) 0(9)b-000)b 2.6812) 0(9)b-cu(3)-0( l0)b 86.3(5) the three anions most affected by this (O(2-4)) have the 0(9)b-0(11)c 3.47t2) 0(9)b-cu(3)-0(I I )c 93.4(5) highesttemperature factors (except for the (HrO)anions). 0(10)b-0(il)c 3.36(2) 0(l0)b-Cu( 3)-0( I I )c 9r.4(5) <0-0>Cu(3) 3.05 <0-cu(3)-0> 90.2 The Jahn-Teller distortions of the Cu octahedra were earlier.However, it is also interestingthat theseaxial 0(l)d-0(5)e 3.4r(2) 0(I )d-cu(4)-0(5)e 10t.6{5) noted 00 )d-0(6)d 2.94t2) 0(r )d-cu(4)-0(6)d 83.7(5) elongationsof the Cufu octahedraare also an inte$al part 0(l)d-0(7)e 3.04{2) 0(I )d-Cu(4)-0(7)e 88.0(5) 0n )d-000)d 3.r5(2) 0(I )d-cu(4)-0(10)d 93.0(5) of the structural linkage. It is only for very weak M2+-O 0(5)e-0(7)e 2.66t2) 0{5)e-Cu(4)-0(7)e 85.4{s) 0(5)e-0(10)d 2.90l.2) 0(5)e-cu(4)-0(10)d 96.2(5 ) bonds that an (SO4)tetrahedron could link to three octa- 0(5)e-0(ll)e 2.53(r) 0(5)e-Cu(4)-0(I I )e 80.r(5) 0(6)d-0(7)e 2.8312) 0(6)d-Cu(4)-0(7)e92.215) hedrally coordinated divalent cations. This is in accord 0(6)d-000)d 2.66t2) 0(6)d-cu(4)-0(l0)d 86.r(5) with the generalobservation that (T6+04)2- groups only 0(6)d-0(ll)e 3.4212) 0{6)d-Cu(4)-0(ll}e 94.3{5) 0(7)e-0(11)e 3.r5(2) 0(7 )e-cu (4 )-0( I I )e ul. J{)J link to (M{r) sheetswhen M : Cu2*. 0(10)d-0(ll)e 3.36(2) 0(l0)d-Cu(4) -0( I I )e 93.6(5) <0-0>Cu( <0-Cu(4)-0> 4) 3.01 90.0 Related structures 't07.9( 00 )-0(2) 2.4112) 0(r )-s-o(2) 9) 00)-0(3) 2.43\2) 00)-s-0(3) 109.2(9 ) The [Cu.(SO4XOH)6(HrO)]" sheetthat is the structure o(r )-o(4) 2.3912) 0(r )-s-0(4) I 09.8(9 ) 0(2)-0(3) 2.4112') 0(2)-s-0(3) 108.r(9) module in wroewolfeiteis also found in the structuresof 0(2)-0(4) 2.40\2') 0(2)-s-0(4) 1il.4(9) posnjakite and langite. Note that the structure module in 0(3)-0(4) 2.40\2) 0(3) -s-0(4) 110.4(9) <0-0> 5 ?.41 <0-s-0> r09.5 this seriesof mineralsis not topologicallycentrosymmetric, and these three minerals do have non-centrosymmetric Hydrogenbonds: donor-acceptor contacts spacegroups. 0(5)-0(12) 2.7212) 0(6)-0il) 2.9412) 0(6)-0(2) 2.87t2) Mellini and Merlino (1979)also relatedposnjakite to the 0(7)-0(2) ?.9912) structures of ktenasite, serpierite and devillite (Table 6). 0(8)-0(3) 2.90\2) 0(9)-0(4) 2.831?) These structures are based on the structure module HAWTHORNE AND GROAT: STRUCTURE OF WROEWOLFEITE 1053

Table 5. Empirical bond-valence*table for wroewolfeite

Cu(l) Cu(2)Cu(3) Cu(4) S H(5) H(6) H(7) H(8) H(9) H(10)rHilr)A H(il)B H(r2)A Hn2)B

0(l ) 0.1?6 0.171 0.r 33 r .431 0.r05 (0.089) 1.966(2.055) 0l2l I .469 0.1050.142 0.205 |.92r ,l.953 0(3) I .435 0.185 0.128 0.205 0(4) I .738 0.218{0.089) 1.956(2.045)

0(5) 0.390 0.468 0.7r8 2.0 0(6) 0.4r0 0.376 0.790 2.0 0(7) 0.r48 0.5t6 0.424 0.858 ?.0

0(8) 0.390 0.375 0.420 0.424 0.815 2.0 0(9) 0.386 0.439 0.393 0.478 0.782 2.0 000) 0.137 0.5r8 0.523 0.822 ?.0 0(lr) 0.I l7 0.064 0.075 0.872 0.872 ?.0 0fi2) 0.282 0.r28 0.795 0.195 2.0 '].0 1 1.850 1.912 2.082 2.057 6.073 1.0 1.0 1.0 'Calculated tvalues from the curves of Brown{1981); in Darentheseshave 0H....0 contacts >3.08,

[Cun(SOn)r(OH).]'-, a corrugated octahedral edge- Prediction of inter-module linkage (SOn) sharing sheetwith tetrahedraattached to both sides Certain aspectsof these structures can be interpreted of the sheet,rather than one side as in the wroewolfeite using the ideasof structural Lewis acidity/basicityrelations type structures.This module is centrosymmetric,and the describedby Hawthorne(1985a). The structuremodule of structures based on it do have centrosymmetric space the wroewolfeitestructures is [Cuo(SOn[OH)u(HrO)].The groups. bond-valencerequirements of the (OH) and (HrO) anions These sheets can be written in the general fonn are more than satisfied, and thus one hydrogen bond lMode-,X.], whereM representsa divalentcation, d rep- should emanatefrom each(OH) and two hydrogen bonds resentsa simple anion (O2-, (OH)-, etc.)and X represents from the (HrO) anion. The 02- anions are assumedto a complex anion ((SOo)2-,etc.). The ktenasite structures have a coordination number of [a]. With regard to the have n:2. and the wroewolfeitestructures have n: 1. The copper hydroxy-chloride botallackite (Hawthorne, 1985b)has n : 0, and the formula Cur(OH)rCl. The struc- ture module can be written as [Cun(OH)uClr], and the modulesare linked by hydrogenbonding as in the sulphate structures.

c I b t l<- b ---i Fig. 2. The structure of wroewolfEite projected onto (100); oc- tahedra are hatched, tetrahedra are dotted. Proposed hydrogen atoms are shown as small filled circles. Donor-hydrogen and F-- I -+l hydrogen-acceptor bonds are shown by full and dotted lines re- Fig. 1. The structure of wroewolfeiteprojected onto (001);oc- spectively. The O(12) oxygen atoms are shown as unshaded large tahedraare shaded.tetrahedra are not shaded. circles. 1054 HAWTHORNE AND GROAT: STRUCTURE OF WROEWOLFEITE

Table 6. The [Cu4(SOJ,(OH)6(H2O)r-,](x : 1,2)minerals

lvlineral Formula ar8) ot8t cl8t B(o) Sp.Gr.Ref.

Posnjakite ICuO{S0O)(0H)6(f|20)] 10.578(5)6.345(3) 7.863(3)ll/.98(5) Pa (l)

Langite IcuO(S0O)(0H)6(H20)](H20) /.137(3)6.031(5) ll.217(l) 90.00(l) Pc l2l

Wroewolfeite ICuO(S0O)(0H)6(H20) ] (H20) 6.045(l) 5.646(l) 14.33712],93.39(l ) Pc (3)

Ktenasite Zn(HrO)U[(Cu,Zn)4(S04)Z(0H)6]5.589(l) 6.166(l) ?3.741(7) 95.55(l) P2,/c{4)

Devilfjte Ca(Hro)r[Cuo(S04)2(0H)6]20.870(2) 6.135(2) 2?.191(3J 102.73(?) P?,/c (5) Serpierite ca(HrO),ICuO(S04)2(0H)6]22.186(2) 6.?5ol?l 21.853(2)I 13.36(I ) C2lc (6)

Refere.nces: (1) Mellini qnd Me.rLino (1979); (2) Centseh anrT Webep (1984); (:i) Thi.s stttd,t; (4) MaLLint ond Mcpl:ao ll97Bt: t:) Sahe1li tnd Zorvz: (t9,"): ,rt S.th,1/i pl Ttnca:i (1968) *the cell dimensionapproximately orthogonal to the sheet is underlined

module cations,O(l) is coordinatedby three Cu and one S, that the ktenasitegroup minerals are hydrated,and could whereasO(2), O(3) and O(4) are coordinatedby one S only. be usedto predict the relative degreeof hydration in these Thus the structuremodule requires3 x 3 :9 additional structures. bonds to satisfy the [4] coordination requirements.The module is electrostaticallyneutral, having an ideal Lewis basicity of zero, and the additional required bonds must Acknowledgments obviously come from the hydrogen bonding arrangement. We are pleasedto acknowledgethe help and cooperationof Joe The module ideally will provide (6 x l) + (1 x 2) : 8 hy- Mandarino and Fred Wicks, curators at the Departmentof Min- drogen bonds in posnjakite (six from the hydroxyls and eralogy and Geology, Royal Ontario Museum.Financial support was provided by the Natural Sciencesand EngineeringResearch two from the (HrO) anion) and (5 x 1) + (l x 2) + 2 :9 Council, in the form of a fellowship, an operating grant and a (five hydrogen bonds in wroewolfeite from hydroxyls, two major equipmentgrant to F. C. Hawthorng and by the University from the module (H2O) anion and two from one hydroxyl of Manitob4 in the form of a graduatefellowship to L. A. Groat. the hydrogen bond of which is split by the transformer action of the non-module(HrO) anion); theseagree closely with the ideal number of [9] indicatedabove, and with the References observednumbers of [7] (Mellini and Merlino, 1979)and Brown, I. D. (1981)The bond-valencemethod: an empirical ap [8] or [10] (Table 5) for posnjakite and wroewolfeitere- proach to chemicalstructure and bonding. In M. O'Keefe and spectively. A. Navrotsky, Eds.,Structure and Bonding in Crystals,Vol. II, The ktenasite structures are based on the p. l-30. AcademicPress, New York. D. T. and Liberman,David (1970)Relativistic calculation [Cun(SOn)z(OH)u]t- module, which has a Lewis basicity Cromer, of 2l$ x 3 - 6) : 0.17 v.u. (module charge/numberof re- of anomalousscattering factors for X-rays.Journal of Chemical Physics,53, 1891-1898. quired bonds - number of module hydrogen bonds).Ac- Cromer, D. T. and Mann, J. B. (1968) X-ray scattering factors cording to the valencematching principle, the Lewis acid- computed from numerical Hartree-Fock wave functions. Acta ity of the extra-module cation should be approximately Crystallographica,424, 321-324. equal to the Lewis basicity of the structure module. The Dunn, P. J. and Rouse,R. C. (1975)Wroewolfeite, a new copper Lewis aciditiesof Ca2+ and Zn2+ are 0.29 and 0.36 v.u. sulphatehydroxide hydrate. Mineralogical Magazine, Q, l-5. respectively(Brown, 1981),significantly greater than the Gentsch, Michael and Weber, Kurt (1984) Structure of langite, module basicity of 0.17 v.u.. However, the extra-module Cuo(OH)u | (SO4il. 2H 20. Acta Crystallographica,C40, 1309- cations are partly to completely coordinated by (HrO) 131l. Hawthorne, F. C. (1985a)Towards a structural classificationof anions, and the transformer action of (HrO) (Hawthorne, 'fhe minerals. vrMIvT2d" minerals.American Mineralogist, 70, 1985a)will considerablymodify the actual cation acidity. 455473. For serpieriteand devillite, the actual Lewis acidity of Ca Hawthorne, F. C. (1985b)Refinernent of the crystal structure of :0.2O is 2l(4 x I + 3 x 2\ v.u.,in good agreementwith the botallackite.Mineralogical MagaAne, 49, 85-91. module basicity of 0.17v.u. For ktenasite,the actual Lewis Mellini, Marcello and Merlino, Stefano(1978) Ktenasite, another :9.17 acidity of Zn is 2l(6 x 2) v.u., again matchingthe mineral with l(Cu, Zn)r(OH),Ol- octahedral sheets.Zeit- module basicity.These arguments thus accountfor the fact schrift ftir Kristallographie,147, 129-14O. HAWTHORNE AND GROAT: STRACTURE OF WROEWOLFEITE

Mellini; Marcello and Merlino, Stefano (1979) Posnjakite: Wappler, G. (1971)Zur Kristallstruktur von Langit, Cu4(OH)G/ 1[Cu4(OH)6(H'O)O] sheetsin its sliuarur.e.Zeitschrift fiir Kri- SO4l .H2O. BerichteDeutsche GesellschaftGeologische Wis- stallographie,149, 249157. senschaftenReihe B, 16,175-203. Sabelli, Casere and Zanazzi, P. F. (1968) The crystal structure of serpierite. Acta Crystallogra phica, 824, 1214-1221. Sabelli, Casere and Zana7li, P. F. O97q The crystal structure of Mantscript receioed., September 27, 1984; devillite.Acta Crystallographica,B28, I 182-1f 89. accepted.for publicotion, April 25, 1985.